I ask for help. I always get the message lower left corner "can not complete the task: your license denies this action." I have tried to follow the advice that has been given but with the same result. What should I do in order to use zmodeler?

this message actually means "no license installed". If you've just installed license (or let ZM download license), you should restart ZModeler. Once ZModeler starts with license (you can see a license key in "License Information" window immediately after opening this page), it should be able to open\import\export.